Employee Benefit Plans (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Components of net periodic benefit cost [Abstract]
Cost recognized	$ 39,000	$ 37,000	$ 117,000	$ 103,000
Employer contribution to 401 (k) defined contribution plan	45,000	52,000	193,000	184,000
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized under restricted stock plan (in shares)	100,000		100,000
Number of restricted stock available for grant (in shares)	67,756		67,756
Restricted Stock [Member]
Restricted stock activity [Roll Forward]
Outstanding, beginning of period	7,466	8,507	8,646	9,921
Granted	0	0	3,027	3,808
Forfeited	0	0	(55)	0
Vested	0	0	(4,152)	(5,222)
Outstanding, end of period	7,466	8,507	7,466	8,507
Weighted average market price [Roll Forward]
Outstanding, beginning of period	$ 41.89	$ 35.16	$ 35.51	$ 29.37
Granted	$ 0	$ 0	$ 48.21	$ 37.10
Forfeited	$ 0	$ 0	$ 37.10	$ 0
Vested	$ 0	$ 0	$ 33.26	$ 25.59
Outstanding, end of period	$ 41.89	$ 35.16	$ 41.89	$ 35.16
Directors [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Deferred interest expense	5,000	4,000	12,000	12,000
Pension Plan [Member]
Components of net periodic benefit cost [Abstract]
Service cost	81,000	82,000	258,000	249,000
Interest cost	89,000	85,000	274,000	259,000
Expected return on plan assets	(165,000)	(139,000)	(508,000)	(425,000)
Net amortization and deferral	66,000	34,000	194,000	102,000
Net periodic benefit cost	71,000	62,000	218,000	185,000
Employer contribution to pension plan			1,000,000
Supplemental Executive Retirement Plans [Member]
Components of net periodic benefit cost [Abstract]
Obligation included in other liabilities	1,010,000		1,010,000		901,000
Cost recognized	37,000	23,000	109,000	69,000
Deferred Compensation Plan [Member]
Components of net periodic benefit cost [Abstract]
Obligation included in other liabilities	$ 976,000		$ 976,000		$ 1,001,000